This invention relates to modified, water-dilutable polymer oil imides containing carboxyl groups.
The invention also relates to a process for producing the aforementioned polymer oil imides and to coating compositions, especially for electro-dip-lacquering, which contain these polymer oil imides as a binder. These aqueous coating compositions are prepared by neutralising the aforementioned modified polymer oil imides with a base, followed by gradual dilution with more water, optionally in conjunction with other solvents.
The increasing demands of industry on electro-dip-lacquers in regard to their service properties, coupled with increasing efforts to control pollution, are leading in the lacquer industry to developments which improve coverage and protection against corrosion by using resin systems which, when stoved, give off very little solvent or other pollutants into the atmosphere. Modified, water-dilutable olefin polymer oils containing carboxyl groups are already known, such as those produced by reacting .alpha.,.beta.-unsaturated dicarboxylic acids or their anhydrides, more especially maleic acid anhydride, optionally in admixture with .alpha.,.beta.-unsaturated monocarboxylic acids, and/or (semi) esters and/or (semi) amides of these acids with olefin polymer oils substantially free from carboxyl groups (German Auslegeschrift (DAS) No. 1,929,593). On the other hand, it is known that maleinate oils can be partially converted into imides and the resulting products stoved in combination with phenol-formaldehyde or melamine resin (German Offenlegungsschrift (DOS) No. 1,494,453). On account of their high viscosity, these products are difficult to process by electrophoresis and, when stoved, pollute the surrounding atmosphere to a very considerable extent. In cases where non-phosphatised metal sheets are used, totally unsatisfactory ASTM-results are obtained after 144 hours. The results reported in Table 2 of DOS No. 1,494,453 relate to the use of phosphatised metal sheets. On the other hand, it is know that the aforementioned olefin polymer oils, more especially maleinised butadiene oils, can be used in conjunction with phenolresole carboxylic acids (DAS No. 1,929,593) in order to improve protection against corrosion. However, these products can only be deposited at very low voltages and are extremely sensitive to temperature in their deposition behavior. Use of phenol-formaldehyde resins also endangers the environment to a considerable extent by polluting the effluents during production (phenols, inorganic salts) and the atmosphere during stoving of the films (liberation of formaldehyde).